This invention relates generally to electronic switched capacitor (charge coupled) voltage signal integrated circuits.
There are applications where it is beneficial to process a continuous voltage signal by first periodically sampling the signal and then processing packets of charge with levels that are proportional to the magnitude of the samples. The charge packets are transferred through such a circuit from capacitor to capacitor by a synchronous operation of switches in between the capacitors. One advantage of a switched capacitor circuit is that no resistors are usually required, thereby reducing circuit area and parasitic effects associated with resistors.
However, the predominate use of capacitive elements in such circuits causes impedances at various circuit nodes to be low at higher signal frequencies. Particularly, an input to such a circuit presents a high input capacitance which can result in drawing more current than desired. Therefore, it is a primary and general object of the present invention to provide switched capacitor circuits with a high input impedance, primarily a low input capacitance, without sacrificing the performance of the circuit.